1. Field of the Invention
This invention relates to knives used in surgical procedures; and more particularly to a single use, self-contained, twist resistant surgical knife having a blade locking and retraction mechanism that can be actuated with a one-hand following knife use to prevent its reuse and impede transmission of blood borne diseases such as AIDS.
2. Description of the Prior Art
Retractable knifes have heretofore been designed which allow extension of the knife blade and retraction of the blade into a handle. U.S. Pat. No. 845,792 to Jenkins, discloses a knife which is retractable within the handle by pushing against a spring, and is locked in place using a pin. The knife is released from the handle by the compressive forces of the spring when the pin is released. Such a knife does not prevent subsequent usage, and the blade is not securely held to prevent lateral displacements and twisting. U.S. Pat. No. 1,424,221 to Trumpeter discloses an ice pick, which is retractable into the handle against a spring and can be locked in the ice pick point exposed or retracted within the handle. A tubular nut secures the pick point in a hidden condition, within the handle, or an exposed condition, outside the handle. Owing to its mechanism, the ice pick does not prevent subsequent usage, and its blade is not securely held to prevent lateral displacements and twisting. U.S. Pat. No. 2,512,237 to Mravik discloses a pocket implement wherein a blade is retracted within a flattened cylindrical sheath enclosure to facilitate carrying the implement in a pocket or handbag. The blade is exposed by pushing the sheath into the handle against a spring, and is held in place by a catching mechanism. The flattened cylindrical sheath provides very limited support for the blade, allowing lateral movement and twisting of the blade. Such a mechanism permits multiple use of the blade. U.S. Pat. No. 3,906,626 to Riuli discloses a unitary disposable surgical scalpel. The scalpel is supplied with the blade exposed. After use it is pushed into a sheath and permanently locked, after which the scalpel is disposed. Once locked, the sheath cannot be removed without completely destroying the sheath. The surgeon essentially holds the sheath to use the knife. A loose fit between the sheath and the retractable blade allows twisting of the blade, preventing precise use of the surgical blade. U.S. Pat. No. 5,330,492 to Haugen discloses a safety scalpel attached to the forward end of a handle. A spring biased retractable sheath is positioned within the handle. Depressing a single button, which pushes the sleeve against the blade, actuates the blade retraction action. The knife can be reused many times and can be withdrawn from the sleeve. It is therefore not a single use device. The blade is handled by using the sleeve, causing lateral and twist instability of the blade during use. U.S. Pat. No. 5,417,704 to Wonderley discloses a disposable surgical scalpel with a U shaped plastic safety guard. The blade is carried on one end of the handle and a plastic safety guard is slid cover over the blade in a protective position or moved away to expose the blade. Displacing the guard beyond a wedge permanently locks the knife. This patented device is a disposable surgical scalpel with a U shaped guard that can be positioned in one of three positions. The U shaped guard can be moved rear-wise to expose the blade, displaced forward to temporarily protect the blade and displaced all the way forward to permanently lock the scalpel. Due to the existence of the intermediate position, the scalpel is not a single use self-contained surgical knife. The U shaped guard has to be slid over a wedge to permanently lock the wedge. Such sliding action may require substantial force, raising the possibility of knife slippage and injury to the surgeon. Since the knife is handled using the guard, the sloppiness between the blade and the U shaped guard causes lateral and twisting displacements of the blade. U.S. Pat. No. 5,556,409 to Haining discloses a disposable scalpel with a retractable blade. The blade can be positioned in an intermediate retracted position for shipping; a fully exposed position for use; and a permanently retracted position for safe disposal. The blade handle has a chamber with projections and a blade carrier having a flexible member which engages with the projections to secure the blade in these three positions. Pressing a tap with the finger controls the blade motion. The tap is sealed once the blade is retracted. This disposable surgical scalpel can move the blade in one of three positions. The blade is moved by pressing on a tap with a finger and this allows sliding if a blade carrier is inside the chamber in the handle. Since the carrier has to slide in the chamber over the projections by finger pressure, there is a degree of loose tolerance between the width of the blade carrier and the width of the chamber, allowing twisting motion of the blade. This loose tolerance prevents precise cutting action by the surgeon. Also this device can be used many times by sliding between the use position and the shipping position, preventing its applicability as a single use device. Also the sliding force needed to lock the blade may accidentally cause injury to the surgeon due to slippage. U.S. Pat. No. 5,741,288 to Rife discloses a rearmable single user safety finger stick device having a reset for multiple use by a single patient. A lancet is extended beyond a hole in the body of the device upon actuation to create a small incision to extract a drop of blood for self-test. Upon arming, the lancet carrier is withdrawn storing energy in a spring in the body of the device. When the lancet is released by pressing a button, the lancet extends outward through a hole in the body over which the user's finger is placed to create the incision. This device is a lancet and is not a single use self-contained surgical knife. U.S. Pat. No. 5,779,724 to Wemer discloses a retractable surgical knife. The device is similar to a ball pen in construction wherein the blade is pushed out by pressing a latch mechanism and retracted by again by pushing on the latch mechanism. The blade is carried in a central carrier and is prevented from falling out. A new scalpel blade can be attached into the device as shown in col. 9 lines 40–50. The blade support assembly is pushed forward to expose the blade and the push button is pushed transversely to retract the blade. Such a device is not a single use, self-contained surgical knife. It is not stable and presents problems during operation, since the blade tends to move laterally and twists due to loose tolerances with which the blade is held in the device containment. U.S. Pat. No. 5,908,432 to Pan discloses a scalpel having a retractable blade. The blade is retained in a blade holder and is slidable within a channel in the distal section of the handle. Such sliding action essentially guards the blade from accidental contact. The retraction function is actuated when the surgeon pushes a spring-loaded button. Such a blade is an actuated, retractable blade that swings into a channel in the handle. This mechanism does not permit the surgical knife to provide a single use, self-contained function. Moreover, loose tolerances between the blade and the handle cause lateral and twist instability of the blade during surgical use. U.S. Pat. No. 6,022,364 to Flumene et al. discloses a disposable surgical safety scalpel. The blade and blade support act as a slider in a shell, and are guided by the shell walls while extending into the in-use position or retracting into the shell. When the blade is extended, the spring in the handle is stretched to produce tension against a pin. During actuation of the pin, tension in the spring is released retracting the blade into the sheath. FIGS. 2 and 4 of U.S. Pat. No. 6,022,364 indicate the position of the spring in the blade retracted and blade exposed conditions. This is not a single use self-contained surgical knife, since the blade can be retracted and brought back into operating position repeatedly. Due to the large area over which the blade holder slides against the sides of the shell, a large clearance must be provided to facilitate the extension and retraction of the blade. As a result, the blade is not held rigidly, and it is difficult for the surgeon to produce precise incisions when using the handle to hold the knife.
Knifes and sharp implements which can be retracted have been extensively disclosed by prior art workers. Disclosures exist involving numerous mechanisms for retraction of surgical knives. No disclosure exists concerning a single use self-contained surgical knife. Instead, each of the mechanisms disclosed permits reuse in one form or other Moreover, there is a fundamental conflict between knife retractability and knife twist stability. Knife retractability using spring mechanisms requires that the knife be easily moved by spring tension. The surgeon typically uses a handle to hold the knife, causing instability of the blade due to lateral displacements and twisting of the blade. This twisting motion prevents the surgeon from producing accurate incisions. For this reason, retractable surgical knifes have heretofore not enjoyed widespread use in surgery.
Key factors for improved knife stability require that the surgical blade be supported in all directions. The support mechanism must be such that the blade is still withdrawn using a small spring tension. Previous attempts to provide retraction capability have not produced a surgical knife having this functionality.
As a consequence remains a need in the art for a single use self-contained surgical knife which provides lateral and twist stability. The retraction process of the blade must function reliably, and be actuated by internal mechanisms of the device that are triggered when the surgeon activates or rotates a single knob with one hand. The retraction of the blade must be accomplished without use of excessive force and must completely prevent reuse of the blade, in order to prevent blood borne infections from being transmitted. This need has heretofore not been met by retractable surgical knives previously proposed by prior art workers.